/*
 * Copyright 2012 The Netty Project
 *
 * The Netty Project licenses this file to you under the Apache License,
 * version 2.0 (the "License"); you may not use this file except in compliance
 * with the License. You may obtain a copy of the License at:
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
 * License for the specific language governing permissions and limitations
 * under the License.
 */

package io.netty.util.internal.logging;

/**
 * Creates an {@link InternalLogger} or changes the default factory implementation.  This factory
 * allows you to choose what logging framework Netty should use.  The default factory is {@link
 * Slf4JLoggerFactory}.  If SLF4J is not available, {@link Log4JLoggerFactory} is used.  If Log4J is
 * not available, {@link JdkLoggerFactory} is used.  You can change it to your preferred logging
 * framework before other Netty classes are loaded:
 * <pre>
 * {@link InternalLoggerFactory}.setDefaultFactory({@link Log4JLoggerFactory}.INSTANCE);
 * </pre>
 * Please note that the new default factory is effective only for the classes which were loaded
 * after the default factory is changed.  Therefore, {@link #setDefaultFactory(InternalLoggerFactory)}
 * should be called as early as possible and shouldn't be called more than once.
 */
public abstract class InternalLoggerFactory {

  private static volatile InternalLoggerFactory defaultFactory;

  @SuppressWarnings("UnusedCatchParameter")
  private static InternalLoggerFactory newDefaultFactory(String name) {
    InternalLoggerFactory f;
    try {
      f = new Slf4JLoggerFactory(true);
      f.newInstance(name).debug("Using SLF4J as the default logging framework");
    } catch (Throwable ignore1) {
      try {
        f = Log4JLoggerFactory.INSTANCE;
        f.newInstance(name).debug("Using Log4J as the default logging framework");
      } catch (Throwable ignore2) {
        try {
          f = Log4J2LoggerFactory.INSTANCE;
          f.newInstance(name).debug("Using Log4J2 as the default logging framework");
        } catch (Throwable ignore3) {
          f = JdkLoggerFactory.INSTANCE;
          f.newInstance(name).debug("Using java.util.logging as the default logging framework");
        }
      }
    }
    return f;
  }

  /**
   * Returns the default factory.  The initial default factory is {@link JdkLoggerFactory}.
   */
  public static InternalLoggerFactory getDefaultFactory() {
    if (defaultFactory == null) {
      defaultFactory = newDefaultFactory(InternalLoggerFactory.class.getName());
    }
    return defaultFactory;
  }

  /**
   * Changes the default factory.
   */
  public static void setDefaultFactory(InternalLoggerFactory defaultFactory) {
    if (defaultFactory == null) {
      throw new NullPointerException("defaultFactory");
    }
    InternalLoggerFactory.defaultFactory = defaultFactory;
  }

  /**
   * Creates a new logger instance with the name of the specified class.
   */
  public static InternalLogger getInstance(Class<?> clazz) {
    return getInstance(clazz.getName());
  }

  /**
   * Creates a new logger instance with the specified name.
   */
  public static InternalLogger getInstance(String name) {
    return getDefaultFactory().newInstance(name);
  }

  /**
   * Creates a new logger instance with the specified name.
   */
  protected abstract InternalLogger newInstance(String name);

}
